The immediate treatment group will receive the intervention in the first time period, while the wait-list control group will receive the intervention program during the second time period. Baseline and outcome evaluation will be accessed at three-time points: baseline assessment (1st week), assessment 1-midway (5th week), and assessment 2-final (10th week) in this study.

To establish and develop an efficient program, several theories were implemented into the intervention design to address handwriting problems in children with ASD, including psycho-geometric theory, motor learning theory, and cognitive training theories. The intervention will be delivered in thirty-six activities for visual perceptual, fine motor, and visual motor integration skill training integrated with the unique properties of the Chinese writing system. A total of 12 hours of intervention program will be conducted in eight sessions within four weeks.

The immediate treatment group will receive the intervention in the first time period, while the wait-list control group will receive the intervention program during the second time period. Baseline and outcome evaluation will be accessed at three-time points: baseline assessment (1st week), assessment 1-midway (5th week), and assessment 2-final (10th week) in this study.

To establish and develop an efficient program, several theories were implemented into the intervention design to address handwriting problems in children with ASD, including psycho-geometric theory, motor learning theory, and cognitive training theories. The intervention will be delivered in thirty-six activities for visual perceptual, fine motor, and visual motor integration skill training integrated with the unique properties of the Chinese writing system. A total of 12 hours of intervention program will be conducted in eight sessions within four weeks.

The intervention program was developed and finalized by a group of occupational therapist specialists in the pediatric field. Thirty-six 20-minute activities with twelve activities for each handwriting fundamental skill were designed in this program.

All intervention activities were designed based on the characteristic of Chinese characters and included different types of characters.

The activities designed will also be graded according to the following principle: (1) the similarities between the character given, (2) the complexity of the figure or character in the activities, and (3) the frequency and level of therapist assistance.

Furthermore, a playful and interesting intervention context will also be integratedinto the program with the design of the adventure journey of an astronaut to further facilitate the motivation and participation of the participants in our program.

CHLAC is a self-developed assessment tool to measure handwriting legibility. The participants will be requested to copy the printed 10 Chinese characters to 2*2cm squares on the exam sheet. These Chinese characters were selected from three versions of current mandarin textbooks, and those with high-frequency and around-the-average stroke counts were chosen. These chosen characters were then selected to ensure a similar ratio of each character type in the test. A trained examiner will score the character legibility according to handwriting legibility and amounts of incorrect strokes. The handwriting legibility dimensions include size, position, orientation, proportion, and space. The total score for handwriting legibility will be 50, and a higher score indicates more legible handwriting. The incorrect strokes will also be counted; a higher score indicates less legible handwriting.

The BCBL is a standardized assessment to evaluate Chinese reading and writing skills. It consists of reading and writing tests. Only the copying subtest will be administered in this study to measure the handwriting speed of participants. In this test, the participant is requested to correctly and accurately copy 25 Chinese characters printed on the exam sheet (near copy subtest and 25 Chinese characters displayed on a cloth strip (far copy subtest). The number of correct characters written within the prescribed time will be calculated and converted into character copy per minute to represent their handwriting speed.

Beery-Buktenica Developmental Test of Visual-Motor Integration - Sixth Edition (VMI-6) is a standardized, norm-referenced assessment to measure the integration level between visual and motor systems of an individual using geometric figure copying tasks. Only the full-form test will be administered in our study. The participants were requested to copy the geometric figure printed, and a trained examiner will score the results according to the criteria given in the scoring sheet. A higher score on this test will represent a better visual-motor integration skill.